Shift work at the atomic level
A new device allows materials scientists to observe in real time the sputtering process used to deposit atomic coatings on surfaces. Although this technique has been used for a long time, until now it has not been possible to follow the process itself. John Bilello and Steven Yalisove of the University of Michigan built the instrument to observe the process of atomization (known in the art as sputtering) - a method of "spray painting" surfaces with thin layers of atoms. Atomization is a common method of coating materials to add strength and protect against corrosion, friction, wear and temperature. The technology is used in a wide range of areas, from microelectronics to protecting the turbine blades in jet engines.
In 1995, the first researchers began making "pinstripe" coatings - patterns of alternating thick and thin nanolayers that dramatically improve material thickness and strength. These so-called multiscalar microstructures are now attracting more and more attention. However, their production requires the highest precision, and that is difficult to achieve. At least in the past it was impossible to check the process before the coating was complete.
The researchers' new development now makes it possible to follow how the atoms arrange themselves on the surface in real time. To do this, they are irradiated with high-intensity X-rays, which they partially reflect. "No one has been able to measure the properties of the thin films during coating - until now," said Bilello.
According to him, by observing the deposition, scientists may be able to influence the ongoing process. Bilello and Yalisove developed the device for their work with "nebulizer plasmas," where argon ions are shot at solids to vaporize them. This creates a high-energy plasma that coats other metals, ceramics and polymers. Later, Yalisove said, in situ X-ray technology will be widely available. "As X-ray sources become smaller and state-of-the-art detectors improve efficiency, we believe everyone needs such systems to improve production throughput and quality control," he says.
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